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TOMOYO Linux Cross Reference
Linux/include/net/tcp.h

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  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              Definitions for the TCP module.
  7  *
  8  * Version:     @(#)tcp.h       1.0.5   05/23/93
  9  *
 10  * Authors:     Ross Biro
 11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 12  *
 13  *              This program is free software; you can redistribute it and/or
 14  *              modify it under the terms of the GNU General Public License
 15  *              as published by the Free Software Foundation; either version
 16  *              2 of the License, or (at your option) any later version.
 17  */
 18 #ifndef _TCP_H
 19 #define _TCP_H
 20 
 21 #define FASTRETRANS_DEBUG 1
 22 
 23 #include <linux/list.h>
 24 #include <linux/tcp.h>
 25 #include <linux/bug.h>
 26 #include <linux/slab.h>
 27 #include <linux/cache.h>
 28 #include <linux/percpu.h>
 29 #include <linux/skbuff.h>
 30 #include <linux/dmaengine.h>
 31 #include <linux/crypto.h>
 32 #include <linux/cryptohash.h>
 33 #include <linux/kref.h>
 34 
 35 #include <net/inet_connection_sock.h>
 36 #include <net/inet_timewait_sock.h>
 37 #include <net/inet_hashtables.h>
 38 #include <net/checksum.h>
 39 #include <net/request_sock.h>
 40 #include <net/sock.h>
 41 #include <net/snmp.h>
 42 #include <net/ip.h>
 43 #include <net/tcp_states.h>
 44 #include <net/inet_ecn.h>
 45 #include <net/dst.h>
 46 
 47 #include <linux/seq_file.h>
 48 #include <linux/memcontrol.h>
 49 
 50 extern struct inet_hashinfo tcp_hashinfo;
 51 
 52 extern struct percpu_counter tcp_orphan_count;
 53 extern void tcp_time_wait(struct sock *sk, int state, int timeo);
 54 
 55 #define MAX_TCP_HEADER  (128 + MAX_HEADER)
 56 #define MAX_TCP_OPTION_SPACE 40
 57 
 58 /* 
 59  * Never offer a window over 32767 without using window scaling. Some
 60  * poor stacks do signed 16bit maths! 
 61  */
 62 #define MAX_TCP_WINDOW          32767U
 63 
 64 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
 65 #define TCP_MIN_MSS             88U
 66 
 67 /* The least MTU to use for probing */
 68 #define TCP_BASE_MSS            512
 69 
 70 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 71 #define TCP_FASTRETRANS_THRESH 3
 72 
 73 /* Maximal reordering. */
 74 #define TCP_MAX_REORDERING      127
 75 
 76 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
 77 #define TCP_MAX_QUICKACKS       16U
 78 
 79 /* urg_data states */
 80 #define TCP_URG_VALID   0x0100
 81 #define TCP_URG_NOTYET  0x0200
 82 #define TCP_URG_READ    0x0400
 83 
 84 #define TCP_RETR1       3       /*
 85                                  * This is how many retries it does before it
 86                                  * tries to figure out if the gateway is
 87                                  * down. Minimal RFC value is 3; it corresponds
 88                                  * to ~3sec-8min depending on RTO.
 89                                  */
 90 
 91 #define TCP_RETR2       15      /*
 92                                  * This should take at least
 93                                  * 90 minutes to time out.
 94                                  * RFC1122 says that the limit is 100 sec.
 95                                  * 15 is ~13-30min depending on RTO.
 96                                  */
 97 
 98 #define TCP_SYN_RETRIES  6      /* This is how many retries are done
 99                                  * when active opening a connection.
100                                  * RFC1122 says the minimum retry MUST
101                                  * be at least 180secs.  Nevertheless
102                                  * this value is corresponding to
103                                  * 63secs of retransmission with the
104                                  * current initial RTO.
105                                  */
106 
107 #define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
108                                  * when passive opening a connection.
109                                  * This is corresponding to 31secs of
110                                  * retransmission with the current
111                                  * initial RTO.
112                                  */
113 
114 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
115                                   * state, about 60 seconds     */
116 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
117                                  /* BSD style FIN_WAIT2 deadlock breaker.
118                                   * It used to be 3min, new value is 60sec,
119                                   * to combine FIN-WAIT-2 timeout with
120                                   * TIME-WAIT timer.
121                                   */
122 
123 #define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
124 #if HZ >= 100
125 #define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
126 #define TCP_ATO_MIN     ((unsigned)(HZ/25))
127 #else
128 #define TCP_DELACK_MIN  4U
129 #define TCP_ATO_MIN     4U
130 #endif
131 #define TCP_RTO_MAX     ((unsigned)(120*HZ))
132 #define TCP_RTO_MIN     ((unsigned)(HZ/5))
133 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
134 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
135                                                  * used as a fallback RTO for the
136                                                  * initial data transmission if no
137                                                  * valid RTT sample has been acquired,
138                                                  * most likely due to retrans in 3WHS.
139                                                  */
140 
141 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
142                                                          * for local resources.
143                                                          */
144 
145 #define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
146 #define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
147 #define TCP_KEEPALIVE_INTVL     (75*HZ)
148 
149 #define MAX_TCP_KEEPIDLE        32767
150 #define MAX_TCP_KEEPINTVL       32767
151 #define MAX_TCP_KEEPCNT         127
152 #define MAX_TCP_SYNCNT          127
153 
154 #define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
155 
156 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
157 #define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
158                                          * after this time. It should be equal
159                                          * (or greater than) TCP_TIMEWAIT_LEN
160                                          * to provide reliability equal to one
161                                          * provided by timewait state.
162                                          */
163 #define TCP_PAWS_WINDOW 1               /* Replay window for per-host
164                                          * timestamps. It must be less than
165                                          * minimal timewait lifetime.
166                                          */
167 /*
168  *      TCP option
169  */
170  
171 #define TCPOPT_NOP              1       /* Padding */
172 #define TCPOPT_EOL              0       /* End of options */
173 #define TCPOPT_MSS              2       /* Segment size negotiating */
174 #define TCPOPT_WINDOW           3       /* Window scaling */
175 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
176 #define TCPOPT_SACK             5       /* SACK Block */
177 #define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
178 #define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
179 #define TCPOPT_EXP              254     /* Experimental */
180 /* Magic number to be after the option value for sharing TCP
181  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
182  */
183 #define TCPOPT_FASTOPEN_MAGIC   0xF989
184 
185 /*
186  *     TCP option lengths
187  */
188 
189 #define TCPOLEN_MSS            4
190 #define TCPOLEN_WINDOW         3
191 #define TCPOLEN_SACK_PERM      2
192 #define TCPOLEN_TIMESTAMP      10
193 #define TCPOLEN_MD5SIG         18
194 #define TCPOLEN_EXP_FASTOPEN_BASE  4
195 
196 /* But this is what stacks really send out. */
197 #define TCPOLEN_TSTAMP_ALIGNED          12
198 #define TCPOLEN_WSCALE_ALIGNED          4
199 #define TCPOLEN_SACKPERM_ALIGNED        4
200 #define TCPOLEN_SACK_BASE               2
201 #define TCPOLEN_SACK_BASE_ALIGNED       4
202 #define TCPOLEN_SACK_PERBLOCK           8
203 #define TCPOLEN_MD5SIG_ALIGNED          20
204 #define TCPOLEN_MSS_ALIGNED             4
205 
206 /* Flags in tp->nonagle */
207 #define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
208 #define TCP_NAGLE_CORK          2       /* Socket is corked         */
209 #define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
210 
211 /* TCP thin-stream limits */
212 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
213 
214 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
215 #define TCP_INIT_CWND           10
216 
217 /* Bit Flags for sysctl_tcp_fastopen */
218 #define TFO_CLIENT_ENABLE       1
219 #define TFO_SERVER_ENABLE       2
220 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
221 
222 /* Process SYN data but skip cookie validation */
223 #define TFO_SERVER_COOKIE_NOT_CHKED     0x100
224 /* Accept SYN data w/o any cookie option */
225 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
226 
227 /* Force enable TFO on all listeners, i.e., not requiring the
228  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
229  */
230 #define TFO_SERVER_WO_SOCKOPT1  0x400
231 #define TFO_SERVER_WO_SOCKOPT2  0x800
232 /* Always create TFO child sockets on a TFO listener even when
233  * cookie/data not present. (For testing purpose!)
234  */
235 #define TFO_SERVER_ALWAYS       0x1000
236 
237 extern struct inet_timewait_death_row tcp_death_row;
238 
239 /* sysctl variables for tcp */
240 extern int sysctl_tcp_timestamps;
241 extern int sysctl_tcp_window_scaling;
242 extern int sysctl_tcp_sack;
243 extern int sysctl_tcp_fin_timeout;
244 extern int sysctl_tcp_keepalive_time;
245 extern int sysctl_tcp_keepalive_probes;
246 extern int sysctl_tcp_keepalive_intvl;
247 extern int sysctl_tcp_syn_retries;
248 extern int sysctl_tcp_synack_retries;
249 extern int sysctl_tcp_retries1;
250 extern int sysctl_tcp_retries2;
251 extern int sysctl_tcp_orphan_retries;
252 extern int sysctl_tcp_syncookies;
253 extern int sysctl_tcp_fastopen;
254 extern int sysctl_tcp_retrans_collapse;
255 extern int sysctl_tcp_stdurg;
256 extern int sysctl_tcp_rfc1337;
257 extern int sysctl_tcp_abort_on_overflow;
258 extern int sysctl_tcp_max_orphans;
259 extern int sysctl_tcp_fack;
260 extern int sysctl_tcp_reordering;
261 extern int sysctl_tcp_dsack;
262 extern int sysctl_tcp_wmem[3];
263 extern int sysctl_tcp_rmem[3];
264 extern int sysctl_tcp_app_win;
265 extern int sysctl_tcp_adv_win_scale;
266 extern int sysctl_tcp_tw_reuse;
267 extern int sysctl_tcp_frto;
268 extern int sysctl_tcp_low_latency;
269 extern int sysctl_tcp_dma_copybreak;
270 extern int sysctl_tcp_nometrics_save;
271 extern int sysctl_tcp_moderate_rcvbuf;
272 extern int sysctl_tcp_tso_win_divisor;
273 extern int sysctl_tcp_mtu_probing;
274 extern int sysctl_tcp_base_mss;
275 extern int sysctl_tcp_workaround_signed_windows;
276 extern int sysctl_tcp_slow_start_after_idle;
277 extern int sysctl_tcp_max_ssthresh;
278 extern int sysctl_tcp_thin_linear_timeouts;
279 extern int sysctl_tcp_thin_dupack;
280 extern int sysctl_tcp_early_retrans;
281 extern int sysctl_tcp_limit_output_bytes;
282 extern int sysctl_tcp_challenge_ack_limit;
283 extern unsigned int sysctl_tcp_notsent_lowat;
284 extern int sysctl_tcp_min_tso_segs;
285 
286 extern atomic_long_t tcp_memory_allocated;
287 extern struct percpu_counter tcp_sockets_allocated;
288 extern int tcp_memory_pressure;
289 
290 /*
291  * The next routines deal with comparing 32 bit unsigned ints
292  * and worry about wraparound (automatic with unsigned arithmetic).
293  */
294 
295 static inline bool before(__u32 seq1, __u32 seq2)
296 {
297         return (__s32)(seq1-seq2) < 0;
298 }
299 #define after(seq2, seq1)       before(seq1, seq2)
300 
301 /* is s2<=s1<=s3 ? */
302 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
303 {
304         return seq3 - seq2 >= seq1 - seq2;
305 }
306 
307 static inline bool tcp_out_of_memory(struct sock *sk)
308 {
309         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
310             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
311                 return true;
312         return false;
313 }
314 
315 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
316 {
317         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
318         int orphans = percpu_counter_read_positive(ocp);
319 
320         if (orphans << shift > sysctl_tcp_max_orphans) {
321                 orphans = percpu_counter_sum_positive(ocp);
322                 if (orphans << shift > sysctl_tcp_max_orphans)
323                         return true;
324         }
325         return false;
326 }
327 
328 extern bool tcp_check_oom(struct sock *sk, int shift);
329 
330 /* syncookies: remember time of last synqueue overflow */
331 static inline void tcp_synq_overflow(struct sock *sk)
332 {
333         tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
334 }
335 
336 /* syncookies: no recent synqueue overflow on this listening socket? */
337 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
338 {
339         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
340         return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
341 }
342 
343 extern struct proto tcp_prot;
344 
345 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
346 #define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
347 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
348 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
349 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
350 
351 extern void tcp_init_mem(struct net *net);
352 
353 extern void tcp_tasklet_init(void);
354 
355 extern void tcp_v4_err(struct sk_buff *skb, u32);
356 
357 extern void tcp_shutdown (struct sock *sk, int how);
358 
359 extern void tcp_v4_early_demux(struct sk_buff *skb);
360 extern int tcp_v4_rcv(struct sk_buff *skb);
361 
362 extern int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
363 extern int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
364                        size_t size);
365 extern int tcp_sendpage(struct sock *sk, struct page *page, int offset,
366                         size_t size, int flags);
367 extern void tcp_release_cb(struct sock *sk);
368 extern void tcp_wfree(struct sk_buff *skb);
369 extern void tcp_write_timer_handler(struct sock *sk);
370 extern void tcp_delack_timer_handler(struct sock *sk);
371 extern int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
372 extern int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
373                                  const struct tcphdr *th, unsigned int len);
374 extern void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
375                                 const struct tcphdr *th, unsigned int len);
376 extern void tcp_rcv_space_adjust(struct sock *sk);
377 extern void tcp_cleanup_rbuf(struct sock *sk, int copied);
378 extern int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
379 extern void tcp_twsk_destructor(struct sock *sk);
380 extern ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
381                                struct pipe_inode_info *pipe, size_t len,
382                                unsigned int flags);
383 
384 static inline void tcp_dec_quickack_mode(struct sock *sk,
385                                          const unsigned int pkts)
386 {
387         struct inet_connection_sock *icsk = inet_csk(sk);
388 
389         if (icsk->icsk_ack.quick) {
390                 if (pkts >= icsk->icsk_ack.quick) {
391                         icsk->icsk_ack.quick = 0;
392                         /* Leaving quickack mode we deflate ATO. */
393                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
394                 } else
395                         icsk->icsk_ack.quick -= pkts;
396         }
397 }
398 
399 #define TCP_ECN_OK              1
400 #define TCP_ECN_QUEUE_CWR       2
401 #define TCP_ECN_DEMAND_CWR      4
402 #define TCP_ECN_SEEN            8
403 
404 enum tcp_tw_status {
405         TCP_TW_SUCCESS = 0,
406         TCP_TW_RST = 1,
407         TCP_TW_ACK = 2,
408         TCP_TW_SYN = 3
409 };
410 
411 
412 extern enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
413                                                      struct sk_buff *skb,
414                                                      const struct tcphdr *th);
415 extern struct sock * tcp_check_req(struct sock *sk,struct sk_buff *skb,
416                                    struct request_sock *req,
417                                    struct request_sock **prev,
418                                    bool fastopen);
419 extern int tcp_child_process(struct sock *parent, struct sock *child,
420                              struct sk_buff *skb);
421 extern void tcp_enter_loss(struct sock *sk, int how);
422 extern void tcp_clear_retrans(struct tcp_sock *tp);
423 extern void tcp_update_metrics(struct sock *sk);
424 extern void tcp_init_metrics(struct sock *sk);
425 extern void tcp_metrics_init(void);
426 extern bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst, bool paws_check);
427 extern bool tcp_remember_stamp(struct sock *sk);
428 extern bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
429 extern void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
430 extern void tcp_disable_fack(struct tcp_sock *tp);
431 extern void tcp_close(struct sock *sk, long timeout);
432 extern void tcp_init_sock(struct sock *sk);
433 extern unsigned int tcp_poll(struct file * file, struct socket *sock,
434                              struct poll_table_struct *wait);
435 extern int tcp_getsockopt(struct sock *sk, int level, int optname,
436                           char __user *optval, int __user *optlen);
437 extern int tcp_setsockopt(struct sock *sk, int level, int optname,
438                           char __user *optval, unsigned int optlen);
439 extern int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
440                                  char __user *optval, int __user *optlen);
441 extern int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
442                                  char __user *optval, unsigned int optlen);
443 extern void tcp_set_keepalive(struct sock *sk, int val);
444 extern void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
445 extern int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
446                        size_t len, int nonblock, int flags, int *addr_len);
447 extern void tcp_parse_options(const struct sk_buff *skb,
448                               struct tcp_options_received *opt_rx,
449                               int estab, struct tcp_fastopen_cookie *foc);
450 extern const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
451 
452 /*
453  *      TCP v4 functions exported for the inet6 API
454  */
455 
456 extern void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
457 void tcp_v4_mtu_reduced(struct sock *sk);
458 extern int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
459 extern struct sock * tcp_create_openreq_child(struct sock *sk,
460                                               struct request_sock *req,
461                                               struct sk_buff *skb);
462 extern struct sock * tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
463                                           struct request_sock *req,
464                                           struct dst_entry *dst);
465 extern int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
466 extern int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
467                           int addr_len);
468 extern int tcp_connect(struct sock *sk);
469 extern struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
470                                         struct request_sock *req,
471                                         struct tcp_fastopen_cookie *foc);
472 extern int tcp_disconnect(struct sock *sk, int flags);
473 
474 void tcp_connect_init(struct sock *sk);
475 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
476 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
477 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
478 
479 /* From syncookies.c */
480 extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
481 extern int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
482                              u32 cookie);
483 extern struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, 
484                                     struct ip_options *opt);
485 #ifdef CONFIG_SYN_COOKIES
486 #include <linux/ktime.h>
487 
488 /* Syncookies use a monotonic timer which increments every 60 seconds.
489  * This counter is used both as a hash input and partially encoded into
490  * the cookie value.  A cookie is only validated further if the delta
491  * between the current counter value and the encoded one is less than this,
492  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
493  * the counter advances immediately after a cookie is generated).
494  */
495 #define MAX_SYNCOOKIE_AGE 2
496 
497 static inline u32 tcp_cookie_time(void)
498 {
499         u64 val = get_jiffies_64();
500 
501         do_div(val, 60 * HZ);
502         return val;
503 }
504 
505 extern u32 __cookie_v4_init_sequence(const struct iphdr *iph,
506                                      const struct tcphdr *th, u16 *mssp);
507 extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, 
508                                      __u16 *mss);
509 #else
510 static inline __u32 cookie_v4_init_sequence(struct sock *sk,
511                                             struct sk_buff *skb,
512                                             __u16 *mss)
513 {
514         return 0;
515 }
516 #endif
517 
518 extern __u32 cookie_init_timestamp(struct request_sock *req);
519 extern bool cookie_check_timestamp(struct tcp_options_received *opt,
520                                 struct net *net, bool *ecn_ok);
521 
522 /* From net/ipv6/syncookies.c */
523 extern int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
524                              u32 cookie);
525 extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
526 #ifdef CONFIG_SYN_COOKIES
527 extern u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
528                                      const struct tcphdr *th, u16 *mssp);
529 extern __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
530                                      __u16 *mss);
531 #else
532 static inline __u32 cookie_v6_init_sequence(struct sock *sk,
533                                             struct sk_buff *skb,
534                                             __u16 *mss)
535 {
536         return 0;
537 }
538 #endif
539 /* tcp_output.c */
540 
541 extern void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
542                                       int nonagle);
543 extern bool tcp_may_send_now(struct sock *sk);
544 extern int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
545 extern int tcp_retransmit_skb(struct sock *, struct sk_buff *);
546 extern void tcp_retransmit_timer(struct sock *sk);
547 extern void tcp_xmit_retransmit_queue(struct sock *);
548 extern void tcp_simple_retransmit(struct sock *);
549 extern int tcp_trim_head(struct sock *, struct sk_buff *, u32);
550 extern int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int);
551 
552 extern void tcp_send_probe0(struct sock *);
553 extern void tcp_send_partial(struct sock *);
554 extern int tcp_write_wakeup(struct sock *);
555 extern void tcp_send_fin(struct sock *sk);
556 extern void tcp_send_active_reset(struct sock *sk, gfp_t priority);
557 extern int tcp_send_synack(struct sock *);
558 extern bool tcp_syn_flood_action(struct sock *sk,
559                                  const struct sk_buff *skb,
560                                  const char *proto);
561 extern void tcp_push_one(struct sock *, unsigned int mss_now);
562 extern void tcp_send_ack(struct sock *sk);
563 extern void tcp_send_delayed_ack(struct sock *sk);
564 extern void tcp_send_loss_probe(struct sock *sk);
565 extern bool tcp_schedule_loss_probe(struct sock *sk);
566 
567 /* tcp_input.c */
568 extern void tcp_cwnd_application_limited(struct sock *sk);
569 extern void tcp_resume_early_retransmit(struct sock *sk);
570 extern void tcp_rearm_rto(struct sock *sk);
571 extern void tcp_reset(struct sock *sk);
572 
573 /* tcp_timer.c */
574 extern void tcp_init_xmit_timers(struct sock *);
575 static inline void tcp_clear_xmit_timers(struct sock *sk)
576 {
577         inet_csk_clear_xmit_timers(sk);
578 }
579 
580 extern unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
581 extern unsigned int tcp_current_mss(struct sock *sk);
582 
583 /* Bound MSS / TSO packet size with the half of the window */
584 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
585 {
586         int cutoff;
587 
588         /* When peer uses tiny windows, there is no use in packetizing
589          * to sub-MSS pieces for the sake of SWS or making sure there
590          * are enough packets in the pipe for fast recovery.
591          *
592          * On the other hand, for extremely large MSS devices, handling
593          * smaller than MSS windows in this way does make sense.
594          */
595         if (tp->max_window >= 512)
596                 cutoff = (tp->max_window >> 1);
597         else
598                 cutoff = tp->max_window;
599 
600         if (cutoff && pktsize > cutoff)
601                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
602         else
603                 return pktsize;
604 }
605 
606 /* tcp.c */
607 extern void tcp_get_info(const struct sock *, struct tcp_info *);
608 
609 /* Read 'sendfile()'-style from a TCP socket */
610 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
611                                 unsigned int, size_t);
612 extern int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
613                          sk_read_actor_t recv_actor);
614 
615 extern void tcp_initialize_rcv_mss(struct sock *sk);
616 
617 extern int tcp_mtu_to_mss(struct sock *sk, int pmtu);
618 extern int tcp_mss_to_mtu(struct sock *sk, int mss);
619 extern void tcp_mtup_init(struct sock *sk);
620 extern void tcp_init_buffer_space(struct sock *sk);
621 
622 static inline void tcp_bound_rto(const struct sock *sk)
623 {
624         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
625                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
626 }
627 
628 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
629 {
630         return (tp->srtt >> 3) + tp->rttvar;
631 }
632 
633 extern void tcp_set_rto(struct sock *sk);
634 
635 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
636 {
637         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
638                                ntohl(TCP_FLAG_ACK) |
639                                snd_wnd);
640 }
641 
642 static inline void tcp_fast_path_on(struct tcp_sock *tp)
643 {
644         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
645 }
646 
647 static inline void tcp_fast_path_check(struct sock *sk)
648 {
649         struct tcp_sock *tp = tcp_sk(sk);
650 
651         if (skb_queue_empty(&tp->out_of_order_queue) &&
652             tp->rcv_wnd &&
653             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
654             !tp->urg_data)
655                 tcp_fast_path_on(tp);
656 }
657 
658 /* Compute the actual rto_min value */
659 static inline u32 tcp_rto_min(struct sock *sk)
660 {
661         const struct dst_entry *dst = __sk_dst_get(sk);
662         u32 rto_min = TCP_RTO_MIN;
663 
664         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
665                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
666         return rto_min;
667 }
668 
669 /* Compute the actual receive window we are currently advertising.
670  * Rcv_nxt can be after the window if our peer push more data
671  * than the offered window.
672  */
673 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
674 {
675         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
676 
677         if (win < 0)
678                 win = 0;
679         return (u32) win;
680 }
681 
682 /* Choose a new window, without checks for shrinking, and without
683  * scaling applied to the result.  The caller does these things
684  * if necessary.  This is a "raw" window selection.
685  */
686 extern u32 __tcp_select_window(struct sock *sk);
687 
688 void tcp_send_window_probe(struct sock *sk);
689 
690 /* TCP timestamps are only 32-bits, this causes a slight
691  * complication on 64-bit systems since we store a snapshot
692  * of jiffies in the buffer control blocks below.  We decided
693  * to use only the low 32-bits of jiffies and hide the ugly
694  * casts with the following macro.
695  */
696 #define tcp_time_stamp          ((__u32)(jiffies))
697 
698 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
699 
700 #define TCPHDR_FIN 0x01
701 #define TCPHDR_SYN 0x02
702 #define TCPHDR_RST 0x04
703 #define TCPHDR_PSH 0x08
704 #define TCPHDR_ACK 0x10
705 #define TCPHDR_URG 0x20
706 #define TCPHDR_ECE 0x40
707 #define TCPHDR_CWR 0x80
708 
709 /* This is what the send packet queuing engine uses to pass
710  * TCP per-packet control information to the transmission code.
711  * We also store the host-order sequence numbers in here too.
712  * This is 44 bytes if IPV6 is enabled.
713  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
714  */
715 struct tcp_skb_cb {
716         union {
717                 struct inet_skb_parm    h4;
718 #if IS_ENABLED(CONFIG_IPV6)
719                 struct inet6_skb_parm   h6;
720 #endif
721         } header;       /* For incoming frames          */
722         __u32           seq;            /* Starting sequence number     */
723         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
724         __u32           when;           /* used to compute rtt's        */
725         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
726 
727         __u8            sacked;         /* State flags for SACK/FACK.   */
728 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
729 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
730 #define TCPCB_LOST              0x04    /* SKB is lost                  */
731 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
732 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
733 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
734 
735         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
736         /* 1 byte hole */
737         __u32           ack_seq;        /* Sequence number ACK'd        */
738 };
739 
740 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
741 
742 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
743  *
744  * If we receive a SYN packet with these bits set, it means a network is
745  * playing bad games with TOS bits. In order to avoid possible false congestion
746  * notifications, we disable TCP ECN negociation.
747  */
748 static inline void
749 TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb,
750                 struct net *net)
751 {
752         const struct tcphdr *th = tcp_hdr(skb);
753 
754         if (net->ipv4.sysctl_tcp_ecn && th->ece && th->cwr &&
755             INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield))
756                 inet_rsk(req)->ecn_ok = 1;
757 }
758 
759 /* Due to TSO, an SKB can be composed of multiple actual
760  * packets.  To keep these tracked properly, we use this.
761  */
762 static inline int tcp_skb_pcount(const struct sk_buff *skb)
763 {
764         return skb_shinfo(skb)->gso_segs;
765 }
766 
767 /* This is valid iff tcp_skb_pcount() > 1. */
768 static inline int tcp_skb_mss(const struct sk_buff *skb)
769 {
770         return skb_shinfo(skb)->gso_size;
771 }
772 
773 /* Events passed to congestion control interface */
774 enum tcp_ca_event {
775         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
776         CA_EVENT_CWND_RESTART,  /* congestion window restart */
777         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
778         CA_EVENT_LOSS,          /* loss timeout */
779         CA_EVENT_FAST_ACK,      /* in sequence ack */
780         CA_EVENT_SLOW_ACK,      /* other ack */
781 };
782 
783 /*
784  * Interface for adding new TCP congestion control handlers
785  */
786 #define TCP_CA_NAME_MAX 16
787 #define TCP_CA_MAX      128
788 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
789 
790 #define TCP_CONG_NON_RESTRICTED 0x1
791 #define TCP_CONG_RTT_STAMP      0x2
792 
793 struct tcp_congestion_ops {
794         struct list_head        list;
795         unsigned long flags;
796 
797         /* initialize private data (optional) */
798         void (*init)(struct sock *sk);
799         /* cleanup private data  (optional) */
800         void (*release)(struct sock *sk);
801 
802         /* return slow start threshold (required) */
803         u32 (*ssthresh)(struct sock *sk);
804         /* lower bound for congestion window (optional) */
805         u32 (*min_cwnd)(const struct sock *sk);
806         /* do new cwnd calculation (required) */
807         void (*cong_avoid)(struct sock *sk, u32 ack, u32 in_flight);
808         /* call before changing ca_state (optional) */
809         void (*set_state)(struct sock *sk, u8 new_state);
810         /* call when cwnd event occurs (optional) */
811         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
812         /* new value of cwnd after loss (optional) */
813         u32  (*undo_cwnd)(struct sock *sk);
814         /* hook for packet ack accounting (optional) */
815         void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
816         /* get info for inet_diag (optional) */
817         void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
818 
819         char            name[TCP_CA_NAME_MAX];
820         struct module   *owner;
821 };
822 
823 extern int tcp_register_congestion_control(struct tcp_congestion_ops *type);
824 extern void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
825 
826 extern void tcp_init_congestion_control(struct sock *sk);
827 extern void tcp_cleanup_congestion_control(struct sock *sk);
828 extern int tcp_set_default_congestion_control(const char *name);
829 extern void tcp_get_default_congestion_control(char *name);
830 extern void tcp_get_available_congestion_control(char *buf, size_t len);
831 extern void tcp_get_allowed_congestion_control(char *buf, size_t len);
832 extern int tcp_set_allowed_congestion_control(char *allowed);
833 extern int tcp_set_congestion_control(struct sock *sk, const char *name);
834 extern void tcp_slow_start(struct tcp_sock *tp);
835 extern void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
836 
837 extern struct tcp_congestion_ops tcp_init_congestion_ops;
838 extern u32 tcp_reno_ssthresh(struct sock *sk);
839 extern void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight);
840 extern u32 tcp_reno_min_cwnd(const struct sock *sk);
841 extern struct tcp_congestion_ops tcp_reno;
842 
843 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
844 {
845         struct inet_connection_sock *icsk = inet_csk(sk);
846 
847         if (icsk->icsk_ca_ops->set_state)
848                 icsk->icsk_ca_ops->set_state(sk, ca_state);
849         icsk->icsk_ca_state = ca_state;
850 }
851 
852 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
853 {
854         const struct inet_connection_sock *icsk = inet_csk(sk);
855 
856         if (icsk->icsk_ca_ops->cwnd_event)
857                 icsk->icsk_ca_ops->cwnd_event(sk, event);
858 }
859 
860 /* These functions determine how the current flow behaves in respect of SACK
861  * handling. SACK is negotiated with the peer, and therefore it can vary
862  * between different flows.
863  *
864  * tcp_is_sack - SACK enabled
865  * tcp_is_reno - No SACK
866  * tcp_is_fack - FACK enabled, implies SACK enabled
867  */
868 static inline int tcp_is_sack(const struct tcp_sock *tp)
869 {
870         return tp->rx_opt.sack_ok;
871 }
872 
873 static inline bool tcp_is_reno(const struct tcp_sock *tp)
874 {
875         return !tcp_is_sack(tp);
876 }
877 
878 static inline bool tcp_is_fack(const struct tcp_sock *tp)
879 {
880         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
881 }
882 
883 static inline void tcp_enable_fack(struct tcp_sock *tp)
884 {
885         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
886 }
887 
888 /* TCP early-retransmit (ER) is similar to but more conservative than
889  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
890  */
891 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
892 {
893         tp->do_early_retrans = sysctl_tcp_early_retrans &&
894                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
895                 sysctl_tcp_reordering == 3;
896 }
897 
898 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
899 {
900         tp->do_early_retrans = 0;
901 }
902 
903 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
904 {
905         return tp->sacked_out + tp->lost_out;
906 }
907 
908 /* This determines how many packets are "in the network" to the best
909  * of our knowledge.  In many cases it is conservative, but where
910  * detailed information is available from the receiver (via SACK
911  * blocks etc.) we can make more aggressive calculations.
912  *
913  * Use this for decisions involving congestion control, use just
914  * tp->packets_out to determine if the send queue is empty or not.
915  *
916  * Read this equation as:
917  *
918  *      "Packets sent once on transmission queue" MINUS
919  *      "Packets left network, but not honestly ACKed yet" PLUS
920  *      "Packets fast retransmitted"
921  */
922 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
923 {
924         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
925 }
926 
927 #define TCP_INFINITE_SSTHRESH   0x7fffffff
928 
929 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
930 {
931         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
932 }
933 
934 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
935 {
936         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
937                (1 << inet_csk(sk)->icsk_ca_state);
938 }
939 
940 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
941  * The exception is cwnd reduction phase, when cwnd is decreasing towards
942  * ssthresh.
943  */
944 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
945 {
946         const struct tcp_sock *tp = tcp_sk(sk);
947 
948         if (tcp_in_cwnd_reduction(sk))
949                 return tp->snd_ssthresh;
950         else
951                 return max(tp->snd_ssthresh,
952                            ((tp->snd_cwnd >> 1) +
953                             (tp->snd_cwnd >> 2)));
954 }
955 
956 /* Use define here intentionally to get WARN_ON location shown at the caller */
957 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
958 
959 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
960 extern __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
961 
962 /* The maximum number of MSS of available cwnd for which TSO defers
963  * sending if not using sysctl_tcp_tso_win_divisor.
964  */
965 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
966 {
967         return 3;
968 }
969 
970 /* Slow start with delack produces 3 packets of burst, so that
971  * it is safe "de facto".  This will be the default - same as
972  * the default reordering threshold - but if reordering increases,
973  * we must be able to allow cwnd to burst at least this much in order
974  * to not pull it back when holes are filled.
975  */
976 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
977 {
978         return tp->reordering;
979 }
980 
981 /* Returns end sequence number of the receiver's advertised window */
982 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
983 {
984         return tp->snd_una + tp->snd_wnd;
985 }
986 extern bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight);
987 
988 static inline void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss,
989                                        const struct sk_buff *skb)
990 {
991         if (skb->len < mss)
992                 tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
993 }
994 
995 static inline void tcp_check_probe_timer(struct sock *sk)
996 {
997         const struct tcp_sock *tp = tcp_sk(sk);
998         const struct inet_connection_sock *icsk = inet_csk(sk);
999 
1000         if (!tp->packets_out && !icsk->icsk_pending)
1001                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1002                                           icsk->icsk_rto, TCP_RTO_MAX);
1003 }
1004 
1005 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1006 {
1007         tp->snd_wl1 = seq;
1008 }
1009 
1010 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1011 {
1012         tp->snd_wl1 = seq;
1013 }
1014 
1015 /*
1016  * Calculate(/check) TCP checksum
1017  */
1018 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1019                                    __be32 daddr, __wsum base)
1020 {
1021         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1022 }
1023 
1024 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1025 {
1026         return __skb_checksum_complete(skb);
1027 }
1028 
1029 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1030 {
1031         return !skb_csum_unnecessary(skb) &&
1032                 __tcp_checksum_complete(skb);
1033 }
1034 
1035 /* Prequeue for VJ style copy to user, combined with checksumming. */
1036 
1037 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1038 {
1039         tp->ucopy.task = NULL;
1040         tp->ucopy.len = 0;
1041         tp->ucopy.memory = 0;
1042         skb_queue_head_init(&tp->ucopy.prequeue);
1043 #ifdef CONFIG_NET_DMA
1044         tp->ucopy.dma_chan = NULL;
1045         tp->ucopy.wakeup = 0;
1046         tp->ucopy.pinned_list = NULL;
1047         tp->ucopy.dma_cookie = 0;
1048 #endif
1049 }
1050 
1051 extern bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1052 int tcp_filter(struct sock *sk, struct sk_buff *skb);
1053 
1054 #undef STATE_TRACE
1055 
1056 #ifdef STATE_TRACE
1057 static const char *statename[]={
1058         "Unused","Established","Syn Sent","Syn Recv",
1059         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1060         "Close Wait","Last ACK","Listen","Closing"
1061 };
1062 #endif
1063 extern void tcp_set_state(struct sock *sk, int state);
1064 
1065 extern void tcp_done(struct sock *sk);
1066 
1067 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1068 {
1069         rx_opt->dsack = 0;
1070         rx_opt->num_sacks = 0;
1071 }
1072 
1073 extern u32 tcp_default_init_rwnd(u32 mss);
1074 
1075 /* Determine a window scaling and initial window to offer. */
1076 extern void tcp_select_initial_window(int __space, __u32 mss,
1077                                       __u32 *rcv_wnd, __u32 *window_clamp,
1078                                       int wscale_ok, __u8 *rcv_wscale,
1079                                       __u32 init_rcv_wnd);
1080 
1081 static inline int tcp_win_from_space(int space)
1082 {
1083         return sysctl_tcp_adv_win_scale<=0 ?
1084                 (space>>(-sysctl_tcp_adv_win_scale)) :
1085                 space - (space>>sysctl_tcp_adv_win_scale);
1086 }
1087 
1088 /* Note: caller must be prepared to deal with negative returns */ 
1089 static inline int tcp_space(const struct sock *sk)
1090 {
1091         return tcp_win_from_space(sk->sk_rcvbuf -
1092                                   atomic_read(&sk->sk_rmem_alloc));
1093 } 
1094 
1095 static inline int tcp_full_space(const struct sock *sk)
1096 {
1097         return tcp_win_from_space(sk->sk_rcvbuf); 
1098 }
1099 
1100 static inline void tcp_openreq_init(struct request_sock *req,
1101                                     struct tcp_options_received *rx_opt,
1102                                     struct sk_buff *skb)
1103 {
1104         struct inet_request_sock *ireq = inet_rsk(req);
1105 
1106         req->rcv_wnd = 0;               /* So that tcp_send_synack() knows! */
1107         req->cookie_ts = 0;
1108         tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
1109         tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
1110         tcp_rsk(req)->snt_synack = 0;
1111         req->mss = rx_opt->mss_clamp;
1112         req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
1113         ireq->tstamp_ok = rx_opt->tstamp_ok;
1114         ireq->sack_ok = rx_opt->sack_ok;
1115         ireq->snd_wscale = rx_opt->snd_wscale;
1116         ireq->wscale_ok = rx_opt->wscale_ok;
1117         ireq->acked = 0;
1118         ireq->ecn_ok = 0;
1119         ireq->rmt_port = tcp_hdr(skb)->source;
1120         ireq->loc_port = tcp_hdr(skb)->dest;
1121 }
1122 
1123 extern void tcp_enter_memory_pressure(struct sock *sk);
1124 
1125 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1126 {
1127         return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1128 }
1129 
1130 static inline int keepalive_time_when(const struct tcp_sock *tp)
1131 {
1132         return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1133 }
1134 
1135 static inline int keepalive_probes(const struct tcp_sock *tp)
1136 {
1137         return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1138 }
1139 
1140 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1141 {
1142         const struct inet_connection_sock *icsk = &tp->inet_conn;
1143 
1144         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1145                           tcp_time_stamp - tp->rcv_tstamp);
1146 }
1147 
1148 static inline int tcp_fin_time(const struct sock *sk)
1149 {
1150         int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1151         const int rto = inet_csk(sk)->icsk_rto;
1152 
1153         if (fin_timeout < (rto << 2) - (rto >> 1))
1154                 fin_timeout = (rto << 2) - (rto >> 1);
1155 
1156         return fin_timeout;
1157 }
1158 
1159 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1160                                   int paws_win)
1161 {
1162         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1163                 return true;
1164         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1165                 return true;
1166         /*
1167          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1168          * then following tcp messages have valid values. Ignore 0 value,
1169          * or else 'negative' tsval might forbid us to accept their packets.
1170          */
1171         if (!rx_opt->ts_recent)
1172                 return true;
1173         return false;
1174 }
1175 
1176 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1177                                    int rst)
1178 {
1179         if (tcp_paws_check(rx_opt, 0))
1180                 return false;
1181 
1182         /* RST segments are not recommended to carry timestamp,
1183            and, if they do, it is recommended to ignore PAWS because
1184            "their cleanup function should take precedence over timestamps."
1185            Certainly, it is mistake. It is necessary to understand the reasons
1186            of this constraint to relax it: if peer reboots, clock may go
1187            out-of-sync and half-open connections will not be reset.
1188            Actually, the problem would be not existing if all
1189            the implementations followed draft about maintaining clock
1190            via reboots. Linux-2.2 DOES NOT!
1191 
1192            However, we can relax time bounds for RST segments to MSL.
1193          */
1194         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1195                 return false;
1196         return true;
1197 }
1198 
1199 static inline void tcp_mib_init(struct net *net)
1200 {
1201         /* See RFC 2012 */
1202         TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1203         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1204         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1205         TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1206 }
1207 
1208 /* from STCP */
1209 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1210 {
1211         tp->lost_skb_hint = NULL;
1212 }
1213 
1214 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1215 {
1216         tcp_clear_retrans_hints_partial(tp);
1217         tp->retransmit_skb_hint = NULL;
1218 }
1219 
1220 /* MD5 Signature */
1221 struct crypto_hash;
1222 
1223 union tcp_md5_addr {
1224         struct in_addr  a4;
1225 #if IS_ENABLED(CONFIG_IPV6)
1226         struct in6_addr a6;
1227 #endif
1228 };
1229 
1230 /* - key database */
1231 struct tcp_md5sig_key {
1232         struct hlist_node       node;
1233         u8                      keylen;
1234         u8                      family; /* AF_INET or AF_INET6 */
1235         union tcp_md5_addr      addr;
1236         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1237         struct rcu_head         rcu;
1238 };
1239 
1240 /* - sock block */
1241 struct tcp_md5sig_info {
1242         struct hlist_head       head;
1243         struct rcu_head         rcu;
1244 };
1245 
1246 /* - pseudo header */
1247 struct tcp4_pseudohdr {
1248         __be32          saddr;
1249         __be32          daddr;
1250         __u8            pad;
1251         __u8            protocol;
1252         __be16          len;
1253 };
1254 
1255 struct tcp6_pseudohdr {
1256         struct in6_addr saddr;
1257         struct in6_addr daddr;
1258         __be32          len;
1259         __be32          protocol;       /* including padding */
1260 };
1261 
1262 union tcp_md5sum_block {
1263         struct tcp4_pseudohdr ip4;
1264 #if IS_ENABLED(CONFIG_IPV6)
1265         struct tcp6_pseudohdr ip6;
1266 #endif
1267 };
1268 
1269 /* - pool: digest algorithm, hash description and scratch buffer */
1270 struct tcp_md5sig_pool {
1271         struct hash_desc        md5_desc;
1272         union tcp_md5sum_block  md5_blk;
1273 };
1274 
1275 /* - functions */
1276 extern int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1277                                const struct sock *sk,
1278                                const struct request_sock *req,
1279                                const struct sk_buff *skb);
1280 extern int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1281                           int family, const u8 *newkey,
1282                           u8 newkeylen, gfp_t gfp);
1283 extern int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1284                           int family);
1285 extern struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1286                                          struct sock *addr_sk);
1287 
1288 #ifdef CONFIG_TCP_MD5SIG
1289 extern struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1290                         const union tcp_md5_addr *addr, int family);
1291 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1292 #else
1293 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1294                                          const union tcp_md5_addr *addr,
1295                                          int family)
1296 {
1297         return NULL;
1298 }
1299 #define tcp_twsk_md5_key(twsk)  NULL
1300 #endif
1301 
1302 extern bool tcp_alloc_md5sig_pool(void);
1303 
1304 extern struct tcp_md5sig_pool   *tcp_get_md5sig_pool(void);
1305 static inline void tcp_put_md5sig_pool(void)
1306 {
1307         local_bh_enable();
1308 }
1309 
1310 extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1311 extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1312                                  unsigned int header_len);
1313 extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1314                             const struct tcp_md5sig_key *key);
1315 
1316 /* From tcp_fastopen.c */
1317 extern void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1318                                    struct tcp_fastopen_cookie *cookie,
1319                                    int *syn_loss, unsigned long *last_syn_loss);
1320 extern void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1321                                    struct tcp_fastopen_cookie *cookie,
1322                                    bool syn_lost);
1323 struct tcp_fastopen_request {
1324         /* Fast Open cookie. Size 0 means a cookie request */
1325         struct tcp_fastopen_cookie      cookie;
1326         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1327         size_t                          size;
1328         int                             copied; /* queued in tcp_connect() */
1329 };
1330 void tcp_free_fastopen_req(struct tcp_sock *tp);
1331 
1332 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1333 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1334 extern void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
1335                                     struct tcp_fastopen_cookie *foc);
1336 
1337 #define TCP_FASTOPEN_KEY_LENGTH 16
1338 
1339 /* Fastopen key context */
1340 struct tcp_fastopen_context {
1341         struct crypto_cipher    *tfm;
1342         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1343         struct rcu_head         rcu;
1344 };
1345 
1346 /* write queue abstraction */
1347 static inline void tcp_write_queue_purge(struct sock *sk)
1348 {
1349         struct sk_buff *skb;
1350 
1351         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1352                 sk_wmem_free_skb(sk, skb);
1353         sk_mem_reclaim(sk);
1354         tcp_clear_all_retrans_hints(tcp_sk(sk));
1355 }
1356 
1357 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1358 {
1359         return skb_peek(&sk->sk_write_queue);
1360 }
1361 
1362 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1363 {
1364         return skb_peek_tail(&sk->sk_write_queue);
1365 }
1366 
1367 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1368                                                    const struct sk_buff *skb)
1369 {
1370         return skb_queue_next(&sk->sk_write_queue, skb);
1371 }
1372 
1373 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1374                                                    const struct sk_buff *skb)
1375 {
1376         return skb_queue_prev(&sk->sk_write_queue, skb);
1377 }
1378 
1379 #define tcp_for_write_queue(skb, sk)                                    \
1380         skb_queue_walk(&(sk)->sk_write_queue, skb)
1381 
1382 #define tcp_for_write_queue_from(skb, sk)                               \
1383         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1384 
1385 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1386         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1387 
1388 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1389 {
1390         return sk->sk_send_head;
1391 }
1392 
1393 static inline bool tcp_skb_is_last(const struct sock *sk,
1394                                    const struct sk_buff *skb)
1395 {
1396         return skb_queue_is_last(&sk->sk_write_queue, skb);
1397 }
1398 
1399 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1400 {
1401         if (tcp_skb_is_last(sk, skb))
1402                 sk->sk_send_head = NULL;
1403         else
1404                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1405 }
1406 
1407 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1408 {
1409         if (sk->sk_send_head == skb_unlinked)
1410                 sk->sk_send_head = NULL;
1411         if (tcp_sk(sk)->highest_sack == skb_unlinked)
1412                 tcp_sk(sk)->highest_sack = NULL;
1413 }
1414 
1415 static inline void tcp_init_send_head(struct sock *sk)
1416 {
1417         sk->sk_send_head = NULL;
1418 }
1419 
1420 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1421 {
1422         __skb_queue_tail(&sk->sk_write_queue, skb);
1423 }
1424 
1425 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1426 {
1427         __tcp_add_write_queue_tail(sk, skb);
1428 
1429         /* Queue it, remembering where we must start sending. */
1430         if (sk->sk_send_head == NULL) {
1431                 sk->sk_send_head = skb;
1432 
1433                 if (tcp_sk(sk)->highest_sack == NULL)
1434                         tcp_sk(sk)->highest_sack = skb;
1435         }
1436 }
1437 
1438 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1439 {
1440         __skb_queue_head(&sk->sk_write_queue, skb);
1441 }
1442 
1443 /* Insert buff after skb on the write queue of sk.  */
1444 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1445                                                 struct sk_buff *buff,
1446                                                 struct sock *sk)
1447 {
1448         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1449 }
1450 
1451 /* Insert new before skb on the write queue of sk.  */
1452 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1453                                                   struct sk_buff *skb,
1454                                                   struct sock *sk)
1455 {
1456         __skb_queue_before(&sk->sk_write_queue, skb, new);
1457 
1458         if (sk->sk_send_head == skb)
1459                 sk->sk_send_head = new;
1460 }
1461 
1462 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1463 {
1464         __skb_unlink(skb, &sk->sk_write_queue);
1465 }
1466 
1467 static inline bool tcp_write_queue_empty(struct sock *sk)
1468 {
1469         return skb_queue_empty(&sk->sk_write_queue);
1470 }
1471 
1472 static inline void tcp_push_pending_frames(struct sock *sk)
1473 {
1474         if (tcp_send_head(sk)) {
1475                 struct tcp_sock *tp = tcp_sk(sk);
1476 
1477                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1478         }
1479 }
1480 
1481 /* Start sequence of the skb just after the highest skb with SACKed
1482  * bit, valid only if sacked_out > 0 or when the caller has ensured
1483  * validity by itself.
1484  */
1485 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1486 {
1487         if (!tp->sacked_out)
1488                 return tp->snd_una;
1489 
1490         if (tp->highest_sack == NULL)
1491                 return tp->snd_nxt;
1492 
1493         return TCP_SKB_CB(tp->highest_sack)->seq;
1494 }
1495 
1496 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1497 {
1498         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1499                                                 tcp_write_queue_next(sk, skb);
1500 }
1501 
1502 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1503 {
1504         return tcp_sk(sk)->highest_sack;
1505 }
1506 
1507 static inline void tcp_highest_sack_reset(struct sock *sk)
1508 {
1509         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1510 }
1511 
1512 /* Called when old skb is about to be deleted (to be combined with new skb) */
1513 static inline void tcp_highest_sack_combine(struct sock *sk,
1514                                             struct sk_buff *old,
1515                                             struct sk_buff *new)
1516 {
1517         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1518                 tcp_sk(sk)->highest_sack = new;
1519 }
1520 
1521 /* Determines whether this is a thin stream (which may suffer from
1522  * increased latency). Used to trigger latency-reducing mechanisms.
1523  */
1524 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1525 {
1526         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1527 }
1528 
1529 /* /proc */
1530 enum tcp_seq_states {
1531         TCP_SEQ_STATE_LISTENING,
1532         TCP_SEQ_STATE_OPENREQ,
1533         TCP_SEQ_STATE_ESTABLISHED,
1534         TCP_SEQ_STATE_TIME_WAIT,
1535 };
1536 
1537 int tcp_seq_open(struct inode *inode, struct file *file);
1538 
1539 struct tcp_seq_afinfo {
1540         char                            *name;
1541         sa_family_t                     family;
1542         const struct file_operations    *seq_fops;
1543         struct seq_operations           seq_ops;
1544 };
1545 
1546 struct tcp_iter_state {
1547         struct seq_net_private  p;
1548         sa_family_t             family;
1549         enum tcp_seq_states     state;
1550         struct sock             *syn_wait_sk;
1551         int                     bucket, offset, sbucket, num;
1552         kuid_t                  uid;
1553         loff_t                  last_pos;
1554 };
1555 
1556 extern int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1557 extern void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1558 
1559 extern struct request_sock_ops tcp_request_sock_ops;
1560 extern struct request_sock_ops tcp6_request_sock_ops;
1561 
1562 extern void tcp_v4_destroy_sock(struct sock *sk);
1563 
1564 extern struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
1565                                        netdev_features_t features);
1566 extern struct sk_buff **tcp_gro_receive(struct sk_buff **head,
1567                                         struct sk_buff *skb);
1568 extern int tcp_gro_complete(struct sk_buff *skb);
1569 
1570 extern void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr,
1571                                 __be32 daddr);
1572 
1573 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1574 {
1575         return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1576 }
1577 
1578 static inline bool tcp_stream_memory_free(const struct sock *sk)
1579 {
1580         const struct tcp_sock *tp = tcp_sk(sk);
1581         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1582 
1583         return notsent_bytes < tcp_notsent_lowat(tp);
1584 }
1585 
1586 #ifdef CONFIG_PROC_FS
1587 extern int tcp4_proc_init(void);
1588 extern void tcp4_proc_exit(void);
1589 #endif
1590 
1591 /* TCP af-specific functions */
1592 struct tcp_sock_af_ops {
1593 #ifdef CONFIG_TCP_MD5SIG
1594         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1595                                                 struct sock *addr_sk);
1596         int                     (*calc_md5_hash) (char *location,
1597                                                   struct tcp_md5sig_key *md5,
1598                                                   const struct sock *sk,
1599                                                   const struct request_sock *req,
1600                                                   const struct sk_buff *skb);
1601         int                     (*md5_parse) (struct sock *sk,
1602                                               char __user *optval,
1603                                               int optlen);
1604 #endif
1605 };
1606 
1607 struct tcp_request_sock_ops {
1608 #ifdef CONFIG_TCP_MD5SIG
1609         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1610                                                 struct request_sock *req);
1611         int                     (*calc_md5_hash) (char *location,
1612                                                   struct tcp_md5sig_key *md5,
1613                                                   const struct sock *sk,
1614                                                   const struct request_sock *req,
1615                                                   const struct sk_buff *skb);
1616 #endif
1617 };
1618 
1619 extern int tcpv4_offload_init(void);
1620 
1621 extern void tcp_v4_init(void);
1622 extern void tcp_init(void);
1623 
1624 #endif  /* _TCP_H */
1625 

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